North Carolina Museum of Art

Summary

Constructed in 1982, the four-level, 171,870 sq ft, North Carolina
Museum of Art (NCMA) includes offices, exhibit space and
restaurant/catering operations. Each month, 25,000 visitors view the
NCMA’s collection of treasures, worth in excess of $1 billion. The
museum’s permanent collection spans more than 5,000 years, from
ancient Egypt to the present, making the institution one of the
premier art museums in the Southeast. Conservation experts and
building operators are entrusted to work with the building and its
systems to present and protect the collection for the citizens and
visitors of North Carolina to enjoy now and for generations to come.

Challenge

The North Carolina Museum of Art was experiencing wide fluctuations
in temperature and humidity levels, with swings of 30 percent humidity
in the winter and up to 60 percent in the summer. What might have been
a mere annoyance for another type of facility was a liability for the
museum. Variations in climate could cause canvases to expand and
contract, leading to premature aging, and hinder the museum’s ability
to host national traveling art exhibits with strict environmental
requirements.

Although facility managers knew the state’s
budget did not afford the funds needed for system improvements, they
also knew that without upgrades, the museum could potentially be an
“artificial aging chamber” for its works of art. Besides preserving
its treasures, the museum’s objectives included reducing its
operational costs, energy use and greenhouse gas emissions, as part of
a wider sustainability program.

Solution

Using the North Carolina PC bid process, NCMA requested upgrade
proposals from several design/build suppliers. Based on the proposed
savings, as well as the company’s creative approach and service track
record, the North Carolina Department of Administration awarded Trane
the state’s first capital improvement project funded by recently
enacted performance contracting legislation and processes. Performance
contracting allowed the government-owned facility operators to finance
renovations and improvements based on guaranteed future utility and
operational savings.

Controlling air flow and dew point A modular Trane Climate Changer™ dedicated outside air handling
unit was installed to pretreat, measure and control the airflow and
dew point of the outside air entering the facility. The four existing
constant volume air handlers were converted to variable air volume to
reduce energy consumption. During unoccupied hours, a number of
exhaust fans are cycled off and the airflow is reduced to account for
the reduction in exhaust air from the building.

Centralizing humidity control The dedicated outside air system uses one centralized
high-pressure, high-purity, cold-fog humidification system, replacing
ninety-two distributed steam humidifiers. The new system distributes
the pretreated air to the main air-handling units at a constant 52°F
dew point. With the need for boiler system steam humidification
eliminated, the steam boilers were replaced with a hot water boiler
system.

Top-to-bottom chilled water plant retrofit The museum’s aging chillers and constant speed cooling towers
were replaced with a variable speed chiller plant that includes two
variable frequency drive Trane Earthwise™ CenTraVac™ centrifugal
chillers. The chillers feature reduced evaporator and condenser flows
and variable primary chilled water pumping, with more than 70 percent
evaporator flow turndown. When outside air temperature is at or below
37°F, the chiller compressors are turned off and bypass valves in the
chiller refrigerant circuit are opened to allow refrigerant to
circulate without mechanical compression, satisfying 100 percent of
the museum’s cooling load requirements.

Chiller tower
optimization reduces energy use Chiller and tower controls were upgraded from pneumatic
controls to a direct digital control (DDC) system. The DDC system
saves time by eliminating maintenance of air compressors and
refrigerated air driers, and the need for chart recorders, data
loggers and regular calibration.

Using a Tracer Summit®
building automation system (BAS), museum facilities managers perform
chiller tower optimization to minimize total energy use. This approach
uses outdoor wet-bulb conditions in real time, as well as chiller
loading, to calculate the optimal cooling tower set point.

Results

Backed by a Trane performance contract guarantee, the North Carolina
Museum of Art was able to finance a complete retrofit of its heating
and cooling central plants, air handling and control systems, lighting
and plumbing fixtures. Exceeding the guarantee, the museum is
realizing annual savings of more than $500,000, a 58 percent reduction
from the original utility and operating budgets. Humidity fluctuations
have been drastically reduced to only 5 percent. In addition, system
upgrades have allowed the museum to move from a large to a small
service tariff, reducing energy costs more than $30,000 a year. The
museum now meets the strict “AA” ASHRAE indoor environment
classification requirements and the oftentimes more stringent
requirements of art lending institutions and individuals.

“Without the upgrades, many traveling exhibits, including the American
Chronicles: The Art of Norman Rockwell and Rembrandt, could not come
to the state capital,” says Larry Wheeler, director for the North
Carolina Museum of Art. “This tightly controlled museum environment is
now protecting priceless collections for generations to come.”

About North Carolina Museum of Art

Maintaining temperature and humidity set points is critical for
preserving the North Carolina Museum of Art’s valuable paintings.
Replacing ninety-two distributed steam humidifiers, a centralized
cold-fog system adds humidity to the dedicated outside air unit.